Just One More...
Elastomer Springs Save the
Game
Since translucent roofs on enclosed
baseball stadiums produce too much glare, and opaque roofs
require the installation of odious Astroturf, the architects
of Enron Field, Houston, TX, specified a retractable roof.
However, since other ballparks with such roofs have experienced
many operational glitches, engineers had to develop a new
suspension system to open and close the roof flawlessly.
Traditional "bogie" suspension systems are similar
in construction to the undercarriage of railroad cars, concentrating
the load at a single point when the wheels hit a high spot
on the rail. Uni-Systems, Minneapolis, MN, decided to use
independent suspensions for each of the 142 wheels that carry
the three huge roof sections, thereby allowing each spring
to compress a small amount when its wheel meets a high spot
on the rail. Since the targeted life-span was 25 years, the
concept of using conventional metal springs was dismissed
almost immediately. As designers were already working with
Kastalon Polyurethane Products, Alsip, IL, on a bumper-stop
assembly for the roof system, the idea of using highly resilient,
durable elastomers with exceptional load capacity was examined
as well. They settled upon Adiprene urethane prepolymer from
UniRoyal Chemical, Middlebury, CT.
The resulting cylindrical springs, consisting of alternating
layers of steel and urethane around a central shaft, are only
8 in. in diameter and 9 in. tall, but withstand a normal load
of 125,000 lbs and peak loads up to 325,000 lbs. The urethane
has good extensibility and elasticity while resisting abrasion,
oils, chemicals, ozone and radiation. With this and other
design and materials choices, the initial cost of the suspension
system was cut in half, while saving future maintenance costs.
The 960-ft long roof takes two people to operate and can be
opened or closed in 12 minutes, so that baseball fans can
have air-conditioned comfort while the players enjoy a natural
grass field.
--SG
For more information:
Circle 803 - Uni-Systems Inc,or connect directly
to their website via the Online Reader Service Program
at http://www.OneRS.net/103df-803
Circle 804 - Kastalon Polyurethane Products Inc,
or connect directly at http://www.OneRS.net/103df-804
NDES Booth #7282
Circle 805 - UniRoyal Chemical, a Crompton
business, or connect directly at http://www.OneRS.net/103df-805
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